The art of the present invention relates to electronic protocol converters in general and more particularly to an electronic protocol converter which allows industrial Supervisory Control and Data Acquisition (hereafter referred to as “SCADA”) Systems (also industrial monitoring and control systems) to utilize standard industrial protocols to interrogate viscous fluid or gas meter registers which communicate with Automatic Meter Reading (hereafter referred to as “AMR”) protocols. The present art methods of implementation and associated apparatus provide an interface with and allow interrogation of the encoded meter registers which are typically utilized by municipal utilities in residential and commercial applications. (i.e. water utility companies, gas utility companies, sewer utility companies, etc.) The present art allows conventional industrial SCADA systems to read and utilize meters which are substantially less expensive than conventional industrial milliamp or pulse output flow meters and which provide a nonvolatile totalization of flow. Unlike conventional industrial flow meters which simply provide a 4-20 milliamp current or pulse output which represents a rate of flow, the present art allows retrieval of the total absolute value of fluid which has flowed through the meter (i.e. totalization). The present art does not require the SCADA system to continuously retain a prior volume of fluid flow as the totalization is available directly from the encoded meter registers.
For many years, SCADA (Supervisory Control And Data Acquisition) Systems have relied upon archaic pulse-output and milliamp-output meter registers as the primary data sources for totalization and flow even as “encoded” register technology for AMR (Automatic Meter Reading) has advanced in parallel at an astonishing pace. Due to the significant communication barrier, SCADA integrators have not utilized encoded registers for their systems. That is, encoded registers are designed to transmit their meter readings using AMR protocols, whereas SCADA systems utilize industrial protocols, such as MODBUS® over Ethernet and serial ports. The present art erases this communication barrier and allows SCADA Integrators to collect precise meter readings within water plants, pumping stations, well fields, master meters, and other locations where flow information is required without the undesirable totalization errors that plague pulse technology.
The present art provides industrial SCADA Systems with an improved ability to electronically interrogate the registers of AMR viscous fluid or gas meters, and as a result to provide the SCADA systems with meter readings or totalizations that agree exactly with the reading that is displayed on the meter's physical register. The present art enables each AMR meter to respond as a slave node on an industrial network which communicates with standard industrial protocols such as the MODBUS®, DF1, or ADAM-4000 derived protocols and Raw ASCII protocols. The present art also provides a method and apparatus for differentiating between zero flow conditions and a malfunctioning electronic meter register. The present art further provides a method and apparatus for detecting reverse (backward) flows through a meter. Prior art industrial meters often register a flow output as a milliamp current or pulse output which does not distinguish between forward or backward flows.
In recent years, electronic meter interrogation technology has become divided into approximately two major and distinct categories. The first category (residential and commercial) represents the class of meters which are utilized in residential and commercial facilities for utility company billing purposes. These include end-user water, gas, and electric meters which are interrogated electronically and are used for accounting and billing purposes. The second category (industrial) represents a class of meters which are utilized in industrial process control and monitoring such as pumping station meters, master meters, water plant meters, oil and gas pipeline meters, and well station meters, to name a few. As expected, the first category of meters are produced in very high volumes and are thereby substantially less expensive than the second category. Unfortunately, the electronic communication protocol which the first category residential and commercial meters utilize has heretofore been obscure in publication, difficult to reverse engineer, or non-standardized between various manufactures.
For accounting and billing purposes, residential and commercial electronic meter interrogation technology utilizes both proprietary and non-proprietary AMR (Automatic Meter Reading) protocols to read the meter registers. (hereafter referred to as “encoded registers”) A common physical communication configuration uses three (3) wires: a generally synchronous input clock signal wire, a signal common wire, and an output signal “encoded data” wire. A popular 3-wire encoding protocol is found with the products manufactured by Sensus Metering Systems, Inc. The Sensus® 3-wire protocol is also utilized with the meter registers of several other meter manufacturers, including Badger Meter, Inc., Hersey Meters Company, Inc., Actaris, Inc., Master Meter, Inc., and Metron-Farnier, LLC. An alternate 3-wire protocol has been established by the Neptune Technology Group, Inc. FIG. 1 shows a prior art block form example of residential and commercial meter interrogation for accounting and billing purposes.
For industrial process control and monitoring purposes, electronic meter interrogation technology mainly relies upon pulse or contact per-volume signaling (e.g. one (1) emitted voltage or current pulse per gallon) and current-per-flow signaling (e.g. 4 milliamps=0 gallons per minute, 20 milliamps=500 gallons per minute). The aforementioned register types will hereafter be referred to as “pulse-output” and “milliamp-output” registers, respectively. The reading and monitoring of analog current signals, such as 4-20 milliamp signals, as well as the counting of pulses, is common in industrial controls. An example of a prior art milliamp-output register connected to a SCADA System is shown in FIG. 2; and an example of a prior art pulse-output register connected to a SCADA System is shown in FIG. 3. When rate-of-flow information is desired by a process control system, the use of milliamp-output registers is generally the predominant data acquisition method; whereas, pulse-output registers are the predominant data acquisition method when meter totalization information is desired. Totalization may also be obtained by performing an integral computation of the flow signal with respect to time, but a totalization error of some tangible magnitude would normally occur due to digital integration noise.
Within the industrial monitoring and control arts, prior art meter reading technology that depends upon pulse-output and current-output registers faces significant and inherent challenges in obtaining accurate meter totalizations, especially over long periods of time. For example, to monitor totalization from a pulse-output meter, first the installing technician/engineer must connect the output terminals of the meter to the interrogating control system, which is typically a programmable logic controller (PLC) or remote terminal unit (RTU). Then the technician must program the present reading from the mechanical register into the PLC or RTU. This process is sometimes referred to as “synchronizing the PLC/RTU with the meter”. Theoretically, the PLC/RTU should be able to maintain an accurate count of the pulses, and therefore of the meter reading itself, from this point in time forward. However, in practice, problems often arise. For example, if the PLC/RTU is shut off for any reason while water is flowing through the meter (eg. power outages, equipment failure, broken cable/connector), the PLC/RTU will not be able to count those pulses. This results in the reading on the meter's mechanical register advancing beyond that which is stored within the PLC/RTU. Furthermore, some PLC/RTU equipment does not store the running totalization in non-volatile memory, so upon re-start from a shutdown, the PLC/RTU will erroneously begin its count from zero.
The prior art is further limited in its ability to differentiate the fluid flow direction. If fluid flows in the backward direction, many pulse-output registers will emit pulses with no differentiation for the direction. The same holds true for many milliamp-output registers, as they can emit a positive signal regardless of flow direction. Therefore, the RTU/PLC will interpret these outputs as “forward flow”, and accumulate the totalization count in the wrong (positive) direction. Occasionally, some pulse-output registers emit noise, which can be interpreted by the PLC/RTU as valid pulses, and therefore the accumulated total in the PLC/RTU will be erroneously high.
Over long periods of time, one or more of the aforementioned prior art issues can cause the totalization obtained from the pulse-counting and flow-integrating methods to differ so greatly from the true reading on the internal mechanical register of the meter that it becomes almost unusable. At such times, a technician must be dispatched to re-synchronize the PLC/RTU with the meter. This increases the maintenance, environmental, and other overall costs of the Industrial Control System.
Encoded meter registers (encoded registers) were developed within the past two decades to address the shortcomings of the aforesaid pulse or milliamp output registers. Many encoded registers, such as the E-Coder™ Register by Neptune Technology Group or the ICE™ Register by Sensus Metering Systems, provide a 3-wire interface through which connected equipment may interrogate the register for the exact totalization at any time. Usually, no battery is required within the register, as it only requires power during the meter interrogation process, and it derives all necessary power from the interrogation signal.
Encoded registers electronically communicate meter totalization readings with an accuracy which is far superior to that available from pulse-output and milliamp-output registers. Presently, encoded registers are in wide use as the preferred register type for electronically communicating meter data to residential or commercial utility billing and/or accounting systems. Nevertheless, the aforesaid billing and/or accounting applications collect meter data from the encoded registers through the use of proprietary data collection devices that are tailored for filling billing and accounting databases. None of the aforesaid billing and/or accounting applications utilize, convert to, or format the AMR meter data into generally accepted industrial protocols as does the present art nor do they allow communication with said industrial protocols.
Although industrial control and monitoring systems could also benefit from the superior accuracy of encoded registers, prior to the present art, no devices have existed that were capable of performing the necessary protocol translation between encoded registers and the industrial control and monitoring systems. The present art provides the capability to convert the aforesaid proprietary protocol to that which is utilized within the SCADA framework.
Accordingly, it is an object of the present invention to provide a supervisory control and data acquisition protocol converter capable of reading conventional AMR type encoded registers transmitting Sensus®, Neptune® or other protocols and convert the exact flow and totalization information into a format which is readily accepted by and communicated with industrial monitoring and control systems such as SCADA (Supervisory Control And Data Acquisition) Systems, including but not limited to MODBUS®, ADAM 4000, EtherNet/IP™ and DF1 formats.
Another object of the present invention is to provide a supervisory control and data acquisition protocol converter which is able to sense flow direction information from the encoded registers and provide the SCADA System with properly formatted information regarding amounts and directions of flow.
A further object of the present invention is to provide a supervisory control and data acquisition protocol converter having one or more Electronic Industry Association (EIA) or other serial standards such as RS-232 and RS-485, or Ethernet, or controller-area-network (CAN) industrial monitoring and control system interfaces.
A yet further object of the present invention is to provide a supervisory control and data acquisition protocol converter which is able to mathematically differentiate the encoded registers total value with respect to time in order to provide flow rate information.
A yet further object of the present invention is to provide a supervisory control and data acquisition protocol converter which is capable of accepting conventional pulse and 4-20 milliamp outputs from flow meters and other types of sensors and provide the sensed information in a generally accepted SCADA format.
A yet further object of the present invention is to provide a supervisory control and data acquisition protocol converter which is able to serve a hypertext markup language (html) web page and/or provide a TELNET (telecommunication network) server whereby sensor data information is remotely available via TCP/IP (transmission control protocol/internet protocol) or UDP (universal datagram protocol) links.
A yet further object of the present invention is to provide a supervisory control and data acquisition protocol converter which eliminates the requirement for periodic corrections or synchronizations.
A yet further object of the present invention is to provide a supervisory control and data acquisition protocol converter which promotes energy conservation via the relatively low energy consumption of the apparatus and the absence of previously required physical technician visits for re-synchronization of the meter totalization.
A yet further object of the present invention is to provide a supervisory control and data acquisition protocol converter which assists in the detection of pipeline leaks.